Efficient Gene-Inactivation and Non-Meiotic Allele Introgression in Livestock

Modern genetic techniques are increasing the accuracy with which we can find and select for valuable livestock genetics. But the genetic improvement of livestock is limited by the availability and frequency of identified beneficial alleles, and slowed by linkage disequilibrium and long generation intervals.  Crossbreeding provides an alternative to selective line-breeding, and has historically provided bursts of increased performance due to heterosis and the introgression of beneficial alleles into livestock populations.  The downside of such admixture however is that locally-adapted or purpose-bred genetics can be diluted, requiring additional, lengthy backcrossing to restore utility.  Gene editing can be incorporated into breeding programs to overcome the constraints of linkage disequilibrium and provide the benefits of crossbreeding, without the penalties imposed by whole genome admixture.  The implementation of gene editing could permit the rapid introgression of traits influenced by a few-to-several genes, and can theoretically permit the generation of undiscovered alleles that have dramatic effects on traits that are traditionally difficult to select for. Data describing the efficiency and precision of gene editing in livestock species will be presented.  Non-transgenic application of customized endonucleases for gene inactivation and meiosis-free introgression in livestock will be discussed.